#include <bits/stdc++.h>

using namespace std;
class Solution {
public:
    bool containsDuplicate(vector<int>& nums) 
    {
        unordered_set<int> hash;
        for (auto e : nums)
        {
            if(hash.count(e) != 0)
            {
                return false;
            }
            hash.insert(e);
        }
        return true;
    }
};